One-pot efficient green synthesis of spirooxindole-annulated thiopyran derivatives via Knoevenagel condensation followed by Michael addition

A green, operationally simple and highly efficient one-pot three-component approach for the synthesis of spiro[indoline-3,4′-thiopyrano[2,3-b]indole] derivatives has been developed by the domino reaction of indoline-2-thione, isatin and ethyl cyanoacetate or malononitrile in ethanol at 80 °C for just 20 min. The significant advantages of this protocol are short reaction time, excellent yields, operational simplicity and formation of three new bonds in one operation from easily available starting materials.     

Origin of methyl torsional barrier in 1-methyl-2-(1H)-pyridone

The laser induced fluorescence excitation and single vibronic excitation dispersed fluorescence spectra have been studied for supersonic jet cooled 1-methyl-2(1h)-pyridone. The methyl torsional bands and some low frequency vibrational transitions were assigned for both ground and excited states. The torsional parameters V(3)=244 cm(-1) and V(6)=15 cm(-1) for the ground state and V(3)=164 cm(-1) and V(6)=40 cm(-1) for the excited state were obtained. To get the insight into the methyl torsional barrier, ab initio calculations were performed and compared with the experimental results. Origin of potential barrier was traced by partitioning the barrier energy into changes in bond-antibond interaction, structural, and steric energies accompanying methyl rotation using natural bond orbital analysis. The role of local interactions in ascertaining the barrier potential reveals that its nature cannot be understood without considering the molecular flexing. The hyperconjugation between CHsigma(*) and ring pi(*) observed in lowest unoccupied molecular orbital (LUMO) stabilizes the methyl group conformer that undergoes a 60 degrees rotation in the excited state with respect to that of the ground state, and it is the change in LUMO that plays important role in the excited state barrier formation.     

An optimal network for passenger traffic

The optimal solution of an inter-city passenger transport network has been studied using Zipf’s law for the city populations and the Gravity law describing the fluxes of inter-city passenger traffic. Assuming a fixed value for the cost of transport per person per kilometer we observe that while the total traffic cost decreases, the total wiring cost increases with the density of links. As a result the total cost to maintain the traffic distribution is optimal at a certain link density which vanishes on increasing the network size. At a finite link density the network is scale-free. Using this model the air-route network of India has been generated and an one-to-one comparison of the nodal degree values with the real network has been made.     

A study of frequency and size distribution dependence of extinction for astronomical silicate and graphite grains

It is generally agreed that interstellar dust grains consist of two main components, namely, silicates and graphites. Some models, like MRN model, assume these grains to be homogeneous spheres following a power-law size distribution. This paper presents, in the framework of Mie theory, a parametrization of extinction spectrum curves of the silicates and the graphites separately in terms of frequency and the minimum and maximum of sizes in the distribution. Analytic expressions in ultraviolet and far-ultraviolet are presented for both types of grains. The values of maximum and minimum sizes for which these equations are valid have been identified. These equations can be useful in a number of situations involving silicate and graphite grains.     

An efficient one-pot synthesis of tetrahydrobenzo[a]xanthene-11-one and diazabenzo[a]anthracene-9,11-dione derivatives under solvent free condition

Indium(III) chloride catalyzed one-pot synthesis of 12-aryl/alkyl-8,9,10,12-tetrahydrobenzo[a]xanthene-11-one and 8,10-dimethyl-12-aryl-8,12-dihydro-7-oxa-8,10-diazabenzo[a]anthracene-9,11-dione derivatives have been achieved by three component cyclocondensation of aldehydes, β-naphthol and cyclic 1,3-dicarbonyl compounds under solvent free condition in high yields. P₂O₅ too has been found as an effective catalyst towards this transformation.     

Atom-efficient and environment-friendly multicomponent synthesis of amidoalkyl naphthols catalyzed by P2O5

An atom-efficient and environment-friendly approach for the synthesis of amidoalkyl naphthols (4a-x) via multicomponent one-pot reaction of 2-naphthol (1), aromatic aldehyde (2) and amide (3) catalyzed by P₂O₅ has been developed. The present approach offers several advantages such as reduced reaction times, moderate temperature, higher yields, eco-friendly reaction condition, easy purification and economic availability of the catalyst.     

Concomitant polymorphism of an antiferromagnetically coupled dicopper(II,II) complex with single strand helical assembly: Synthesis,structure, DSC,magnetic and heterogeneous catalytic studies

Two concomitant polymorphic coordination complexes (dark blue – I and black – II) with the formula (Cu₂C₄₄H₆₀N₄O₄) have been synthesized and characterized crystallographically. Magnetic measurements show the presence of a strong antiferromagnetic interaction and the 2J value corresponds extremely well to the theoretically calculated one, indicating the fact that it follows nicely the magneto-structural relationship. Immobilization of the copper(II) complex 1 on a 2D-hexagonal mesoporous silica showed good catalytic efficiency in the liquid phase partial oxidation of olefins in the presence of TBHP as an oxidant.     

A time-of-flight spectrometer for angle-resolved detection of low energy electrons in two dimensions

We have developed a time-of-flight photoelectron spectrometer that simultaneously analyzes low energy electrons photoemitted from solid surfaces in an energy- and angle-resolved manner. To achieve this, a field free drift tube with an acceptance angle of 22° is combined with two-dimensional position-sensitive detection of photoelectrons, which is realized by a microchannel plate stack and a delay-line anode for position encoding. Here, we present the design considerations and principles of operation including analysis of multiple events per light pulse. The performance of the spectrometer is demonstrated by photoemission from a Cu(111) single crystalline surface by UV femtosecond laser pulses at 6.2 eV photon energy. PACS 71.20.-b; 73.20.At; 78.47.J-; 79.60.-i     

Synchronization of coupled stochastic oscillators: The effect of topology

We study sets of genetic networks having stochastic oscillatory dynamics. Depending on the coupling topology we find regimes of phase synchronization of the dynamical variables. We consider the effect of time-delay in the interaction and show that for suitable choices of delay parameter, either in-phase or anti-phase synchronization can occur.